Wireless communication systems are widely deployed to provide various types of communication content, including voice, video, packet data, messaging, and broadcast, among many others. Wireless communication systems (e.g., multiple-access networks that can share available network resources to support multiple users) have developed through various generations, including a first-generation analog wireless phone service (1G), a second-generation (2G) digital wireless phone service (including interim 2.5G and 2.75G networks) and third-generation (3G) and fourth-generation (4G) high speed data/Internet-capable wireless services. There are presently many different wireless communication systems in use, including Cellular and Personal Communications Service (PCS) systems. Example cellular systems include the cellular Analog Advanced Mobile Phone System (AMPS), digital cellular systems based on Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal FDMA (OFDMA), Single-Carrier FDMA (SC-FDMA), the Global System for Mobile access (GSM) TDMA variation, and newer hybrid digital communication systems that use both TDMA and CDMA technologies. More recently, Long Term Evolution (LTE) has been developed as a wireless communication protocol for wireless communication of high-speed data for mobile phones and other data terminals. LTE is based on GSM, and includes contributions from various GSM-related protocols (e.g., Enhanced Data rates for GSM Evolution (EDGE)) and Universal Mobile Telecommunications System (UMTS) protocols (e.g., High-Speed Packet Access (HSPA)).
In general, a wireless communication network may include various base stations (also referred to as evolved node Bs, eNBs, or access nodes) that can support communication for a user equipment (UE). In a WAN, a UE typically communicates via uplink/downlink channels between the UE and a base station to thereby communicate with the base station. However, if two or more UEs are in within sufficient proximity to one another, the UEs may be enabled to communicate directly, that is, without communicating through any base station. A UE may therefore support direct peer-to-peer (P2P) or device-to-device (D2D) communication with one or more other UEs. For example, LTE Direct (LTE-D, sometimes also referred to as “LTE-Advanced”) is a proposed 3GPP (Release 12) D2D solution for proximate discovery. LTE-D dispenses with location tracking and network calls by directly monitoring for services on other LTE Direct devices within a large range (˜500 m, line of sight). As such, among other advantages, LTE-D can directly monitor for services on other LTE-D devices in a synchronous system and concurrently detect many services in proximity in a continuous and battery efficient manner.
LTE-D operates on licensed spectrum as a service to mobile applications and provides D2D solution that enables service layer discovery. Mobile applications on LTE-D devices can instruct LTE-D to monitor for mobile application services on other devices and announce their own services at the physical layer for detection by services on other LTE-D devices, which allows the applications to be closed while LTE-D does the work in a substantially continuous manner and notifies the client application when a match to the monitor is detected. Accordingly, LTE-D is an attractive alternative to mobile developers seeking to deploy proximate discovery solutions to extend their existing services. For example, LTE-D is a distributed discovery solution (versus the centralized discovery that exists today), whereby mobile applications may forego centralized database processing in identifying relevancy matches because relevance may instead be determined autonomously at the device level via transmitting and monitoring for relevant attributes. LTE-D offers additional power consumption benefits because LTE-D does not perpetually track location to determine proximity and privacy benefits because discovery may be kept on the device such that users have more control over information shared with external devices.
Furthermore, LTE-D can increase network efficiency because devices communicate directly using cellular spectrum without utilizing the cellular network infrastructure. As such, because LTE-D uses licensed cellular spectrum, cellular coverage can be extended and interference from other devices can be controlled (unlike D2D communication in unlicensed bands). Accordingly, LTE-D may use direct connections to transfer substantial data between LTE-D enabled devices that are within sufficient proximity, thereby offloading traffic from the network infrastructure. Moreover, in addition to allowing high data transfer rates, LTE-D offers low delays and low energy consumption at the UEs communicating over an LTE-D link. Furthermore, LTE-D offers applications in national security and public safety networks because LTE provides high data rates that can enable real-time data and multimedia exchange between emergency personnel in crisis situations and the D2D functionality can improve performance in LTE-based public safety networks in the event that the LTE infrastructure may be totally or partially disabled (e.g., in disaster scenarios such as earthquakes, hurricanes, terrorist attacks, etc.).
Accordingly, techniques to efficiently support D2D communication are desired to enable new services, improve existing services, eliminate and/or reduce interference, and/or reduce traffic load on network infrastructures, among other things.